This invention is directed to a hydrazine thruster wherein the hydrazine is injected into a catalyst bed and is dissociated whereby hot gas is ejected from a nozzle to produce thrust.
Previous hydrazine dissociation thrusters have experienced problems when operated in a repetitive single pulse mode. For single pulses with long off times between pulses, a prior art thruster will perform normally for a few pulses, but will then perform very much below design levels. After extensive investigation, it was determined that if the catalyst bed is maintained at temperatures exceeding 400.degree. F., all pulses are normal at all on/off time combinations tested. This solution to the pulse degradation problem is undesirable because of the power required for the heater. This solution is also undesirable because the heater is located on the catalyst bed wall and its temperature approaches 2,000.degree. F. during thruster operation. Heaters operating in such an environment are difficult to design and are susceptible to failure. It was discovered during tests using extremely pure hydrazine that such hydrazine limited or, in some cases, overcame the pulse mode degradation problem. Based on this discovery, it was postulated that the small amount of aniline in normal military grade hydrazine deposits on the hydrazine dissociation catalyst at temperatures below 300.degree. F. It was postulated that this deposit poisons the catalyst and prevents it from effectively decomposing the hydrazine. While this postulation was not widely accepted, no previous researcher had been able to prevent thrust degradation for long off-time duty cycles.